The present invention pertains to a container with a coating that inhibits the passage of gaseous and/or liquid substances through the walls of the container, a process for its preparation, and a device for implementing the process.
Containers for storing and conserving gaseous and/or liquid substances are known in the art. Such containers preferably consist of glass or sheet metal sections or plastics, whereby the latter have the advantage (relative to the afore-mentioned materials) of a distinctly lower weight as well as higher resistance to environmental effects. A disadvantageous feature in the case of such plastic containers has proven to be the fact that, with respect to the plastic materials that are currently used, gas exchange takes place via diffusion between the substance present in the container and the outside of the container. The reason for this is that the plastics that are used permit the diffusion of gases such as oxygen, carbon dioxide, or water vapor as well as other volatile substances such as fuels or fragrances and perfumes. The desired long-term stability of the substance in the container is also not guaranteed, especially with the currently available plastic containers.
In order to internally coat hollow containers, consisting of plastic or metal, with inert impermeable glass-like layers, the suggestion is made in WO 95/21948 that inorganic substances be evaporated under vacuum in the interior of the hollow container under the action of a plasma, whereby a certain degree of heating of the container walls by the plasma is desired for better adhesion. A disadvantageous feature is the high expense, in terms of apparatus, for the application and movement of the source for the evaporator.
Alternatively, it is suggested in WO 95/22413 that layers of the same type be prepared in the interior of hollow containers, consisting of plastic or metal, via plasma polymerization, whereby the process pressures inside and outside the container should be controlled independently of one another. The two aforementioned processes have the objective, in particular, of coating the interior of hollow containers, whereby this is less desirable in the case of medicine containers or foodstuffs containers since the reactive behavior of the layers prepared in this way is still almost unknown with respect to the most widely differing contents.
In U.S. Pat. No. 5,374,314, in contrast, a process is proposed for the external coating of hollow objects in which an electrical potential from an electrode, which is also arranged inside the hollow object, acts homogeneously on the interior of the hollow object by means of a first gas, which has been made electrically conductive, within the hollow object. As a result, a coating process is generated on the outside, which is assisted via the use of a second gas that contains charge carriers. However, a disadvantage is the expense, in terms of apparatus, for implementing the process, which is also considerable here.
It is therefore an object of the invention, is to have a container of this type with walls having a low permeability in comparison to known containers.
It is a further object of the invention to have a process for the preparation of such a container and a device for the implementation of the process.